Not exactly sure, but from information I was given many years ago it could well be as Doug says, an engine from 1940-50. Douglas by all accounts produced a series of side valve horizontally opposed twin industrial stationary engines during this period. The information I have gives the following capacities they were produced in namely, 248cc, 463cc, 543cc and 982cc. The engine numbers were prefixed as VS25, VS45, VS55 and VS98 respectively. These numbers would I think be stamped on the lower parts of the crankcase. Never seen an engine as in the photo actually 'in the flesh'. Would be interested in photos taken from all round the engine. At the same time, other engines were produced, with the 348cc ohv air cooled engine ultimately developed into the power unit for the post war motorcycles. These particular engines were also produced in sizes other than 348cc although they were all side valve engines. They were 804cc and 995cc. Together with the 348cc they were prefixed by FT35, FT80 air cooled, FT80W (a water cooled version), FT80M again water cooled with synchromesh gear. Forward 2:1 and reverse 2.14:1. An engine driven generator is fitted and electric starting may be provided. What the set up here is I have no idea. The FT100 was the 995cc s.v air cooled and the FT100W was the 995cc s.v. water cooled version. Apart from this information that was passed on by an ex Douglas employee who worked as a draughtsman at Bristol Aeroplane Company, I have never seen any other information to back this up but there is nothing to doubt the authenticity of what he says. But, someone out there may know differently.....!!!!
[remove bulk quote. -Doug]